A class of E. coli outer membrane proteins called porins have been shown to have a role in the expression of K1 capsule biosynthesis. The rate capsule expression is markedly reduced in porin-negative strains. Newly synthesized K1 capsule was found only at the ends of an E. coli cell. This line lacks the capsule-associated porin protein K1. The acrA mutation in E. coli results in hypersensitivity to a variety of antibiotics. The acrA gene has been cloned and the gene product identified as a component of the cytoplasmic membrane with a molecular weight of about 30,000. The "extracellular" DNAse gene of V. cholerae has been cloned and the gene product identified, although the DNA'se is supposed to be an extracellular enzyme, we find more than 90% of the activity is associated with the cell.